Officially this is not supported, some of the IDB2 records have been changed in size for CA SYSVIEW for DB2 19.0 and they might be truncated during the fallback.
Unofficially there is a method that it should work:
1) Use Release 19.0 IDB2UIFI utility to unload the Release 19.0 History files to SMF.
- Use options /REQ=UNLDHIST,UNLOAD=ALL,REMPOS=NO
- ddnames HISTSTAT and HISTACCT need to be allocated to the Release 19.0 History files.
- SMFOUT needs to be allocated to a VBS dataset.
2) Reload the SMF file produced in Step 1 into a clean LDS files using the previous
Release version of the IDB2UIFI utility.
- use options /REQ=LOADHIST
- SMFIN needs to be allocated to the data set produced in step 1 (SMFOUT).
- HISTSTAT and HISTACCT ddnames must be allocated to the clean history files
(The size should match Release 19.0 versions) for the Release 17.0 version.
The following information might be lost during the procedure: Long IDB2 accounting records (>32K), parallelism rollup details, ...